Control of bisulphite-pulp cooking



Patented Nov. 17, 1925.

UNITED STATES JOSEPH ERNEST FLEURY, OF THREE RIVERS, QUEBEC, CANADA.

CONTROL OF BISULPHITE-PULP COOKING.

N0 Drawing.

T 0 all to 7mm) it may concern:

Be it known that I, JOSEPH ERNESI FLEURY, a subject of the King of GreatBritain, residing at Three Rivers, in the county of St. Maurice andProvince of Quebec, Canada, have invented certain new and usefulImprovements in the Control of B1- sulphite-Pulp Cooking; and I dohereby declare that the following is a full, clear, and exactdescription of the invention, such as will enable others skilled in theart to which it appertains to make and use the same.

This method for the control of bisulphite pulp cooking determinesrapidly the quality of the pulp, guarantees the uniformity of theproduct by giving the exact moment to blow a digester according to thedesired quality of the pulp; or briefly indicates how the cooking isproceeding;

This method is based on the following principle:

The carbohydrates or aldehydes which have a compound action, such assugars, gums, lignins, resins, when in solution turn yellow and thenbrown when they are heated with an alkaline hydroxide, on account of aresinification. However, the great facility with which those alcoholgroups and aldehydes are changed into carboxyls by oxidation, makes itnecessary to stop that reaction by alcoholation.

By testing a sample of the solution in a oolorimeter, I am able todetermine the bleach of the pulp, i. e., the percentage of calcium,hypochlorite containing 35% ac tive chlorine required to bleach the pulpin the digester.

The operation of the invention is as follows: a

When a digester is working, that is, during the reaction, which beginsat 105 C., I take a sample of the liquor, let it be 50 cubiccentimeters, I add 25 cubic centimeters of ammonium hydroxide (one intofive) and 25 cubic centimeters of alcohol (ethyl or methyl) one intoone. Then the liquor takes a colour more or less deep according to thequantity of carbohydrates or aldehydes with a compound action, dissolvedin the liquor at that moment during the cooking.

There is also precipitation of calcium and magnesium monosulphites whichI eliminate by filtration.

The filtrate is compared in a oolorimeter after having been firstdiluted according to the requirements of the oolorimeter used.

Application filed May 14, 1924. Serial No. 713,344.

Knowing beforehand two points on the :colorimeter corresponding to twoqualities of different pulps of which I have found the strength andbleach by several repeated tests, I am able to determine the quality ofthe pulp in the digester and to compare it with the standard. I v

For fixing those two points on the-scale of the oolorimeter, I takesamples of liquors from two blown digesters. I treatthe liquors in theabove manner and examine the filtrate in a Hess-Ives tint oolorimeter.Then I determine the strength and bleach of the two samples of pulp fromthe two digesters, using the Canadian Forest Product Laboratory methods.I find the bleach of the two pulps to be, say, 10% and 9%. I then dilutethe two liquors so that they read 10 and 9 respectively on thecolorimeter with the green glass. The same dilution used in tests ofundetermined samples enables me to read the bleach, at any period of thecooking, directly from the colorimeter. In this manner, the bleach ofthe pulp is easily controlled and the digester may be blown when thedesired bleach has been at tained.

The strength of the pulp is to some extent proportional to the finalbleach, depending, of course, on the condition of the digester atstarting. The strength table can be compiled for a number of sampleswhich have been tested in the oolorimeter at the beginning and end ofthe cooking and also tested for strength by a known method. .A system ofinterpolation for other samples can then be worked out from the table.

Furthermore my method allows one to judge the condition of the cookingand to determine the quality of the pulp, and the right moment to blow adigester with a product conformable to the desired standard. With themethod now commonly in use, which consists in blowing a digester when bytitration with. iodine there is a certain amount of SO present in theliquor, it is practically impossible to have a standard pulp for severalconsecutive digester-s, and the quality of the product is known onlyseveral hours after the digester is blown.

The new method has the advantage of permitting an increased saving ofsteam, and this is due to the fact that the method indicates when thecooking is completed and hence the steam can be shut off.

However, I know'that ammonia has been used for a long time for detectingthe quantity of lime present at the end of the cooking, so thata'certain indication of the condition of the cooking is given; but theprinciple on which my method is based has never been used to determinethe qualities of the pulp; and I am the first to apply the reactionoforganic matters dissolved in the cooking liquor with an alkalinehydroxide, and I am also the first to prevent theformation' of carboxylsby the use of alcohol.

' 'Havingthusfully described the invention, what I claim as new anddesire to protect byLetters Patent is': c I I I 1. Method ofcontrol ofbisulphite pulp cooking'by the colour'of the liquor, consisting indrawing a sample of the liquor from a'digester in operation, to whichsample is added an alkaline hydroxide and an alcohol,

filtering the liquor and diluting it in determined proportion and thencomparing it in a colorimeter With a predetermined graduationcorresponding to certain'percentages of strength and bleach of finishedpulp.

2. Method of controlling bisulphite pulp cooking by the coloration ofthe liquor, consisting in drawing 50 c. c. of liquonfrom a digester inoperation, adding .to this liquor c. c. of ammonium hydroxide (one intofive) and 25 c. c. of alcohol (one to one), then filtering to remove theprecipitate, diluting the filtrate to a. predetermined pro, portiondepending on the coloriineter requirements, and determiningthe qualityof this filtrate with the aid of the colorimeter which has graduationscorresponding to the strength and bleach of two different qualities offinished pulp I J OS. ERNEST FLEURY.

